1. Field of the Invention
The present preferred embodiment relates to a lithography apparatus and, more particularly, to an apparatus which diverts the polarization direction of the incident light beam to at least two different polarization directions.
2. Description of the Prior Art
Lithography process is important in transferring circuit patterns onto a substrate. By projecting a light beam through a photo photomask onto a photoresist, and then exposing, developing, and etching the substrate, the substrate which is uncovered by the photoresist is removed. In this way, a pattern can be transferred onto the remaining substrate. As the integrity of the IC increases, the size of the semiconductor device should be scaled down as well. Therefore, it is an important issue to increase resolution of the lithographic process so as to form a semiconductor device with a smaller size.
A conventional method for improving resolution includes the steps of: off-axis illumination, immersion lithography and increasing the numerical aperture of the lens. In addition, some methods involve adjusting equipment parameters, such as adapting exposure energy and exposure time in order to achieve a better resolution and make a compromise between resolution and depth of focus. However, satisfactory results are not obtained.
Therefore, it is important to develop a lithography apparatus with improved resolution, and compatibility with current equipment.